Herpes zoster in giant cell arteritis: connection or coincidence?

Giant cell arteritis (GCA) is the most common vasculitis among elderly people and has the potential to cause irreversible blindness. The cause of this condition remains unknown. Infectious etiologies have been implicated in the past, with herpes zoster being the most recently postulated. This retrospective study examined whether herpes zoster antigen could be detected in temporal artery biopsies taken from individuals with GCA.

Study design

To explore the possible connection between herpes zoster and GCA, the authors performed immunohistochemistry for herpes zoster antigen on 25 GCA-positive temporal artery biopsies and 25 GCA-negative temporal artery biopsies.

Outcomes

Among the GCA-positive biopsy group, 3 patients had positive staining for herpes zoster antigen, while the antigen was not detected in any biopsies that were negative for GCA. False-positive staining for herpes zoster was noted in areas of calcification, surrounding skeletal muscle and erythrocytes in the temporal artery biopsies.

Limitations

The main limitation of this study was its small sample size. While 1 patient with positive staining for herpes zoster antigen developed GCA within a month of herpes zoster ophthalmicus, the other 2 patients with herpes zoster antigen on biopsy did not have a recent clinical history of herpes zoster. It is possible that these patients could have had zoster sine herpete, but a larger number of patients are required to clarify the connection between herpes zoster and GCA.

Clinical significance

In conclusion, there may be a possible weak association between herpes zoster and GCA. However, the vast majority of people with GCA did not have detectable herpes zoster antigen in the temporal artery biopsies and therefore herpes zoster only contributes to a very small subset of GCA cases. 

It is also important to note that false positive testing for zoster antigen can occur in the setting of calcification and skeletal muscle, which may explain the high positivity of herpes zoster antigen detection in previous studies. In summary, causation has yet to be proven and the verdict is still out as to whether herpes zoster is associated with GCA.